Mitochondria are the organelles within cells responsible for producing adenosine triphosphate, the body's universal energy currency. The average human cell contains hundreds to thousands of mitochondria, and the most energy-demanding tissues, cardiac muscle, skeletal muscle, and neurons, contain the most. Mitochondria have their own DNA, distinct from nuclear DNA, and divide and multiply independently in response to energy demands. The quantity, size, and functional efficiency of mitochondria in a given tissue determines how much energy that tissue can produce and therefore how much sustained physical and cognitive effort is possible.
Mitochondrial Decline with Age
Mitochondrial density in skeletal muscle decreases progressively with age, and this decline is independent of, though accelerated by, physical inactivity. Mitochondrial DNA accumulates mutations over time due to proximity to reactive oxygen species produced during energy generation, and damaged mitochondria become less efficient at producing ATP. Reduced mitochondrial function is now regarded as one of the central mechanisms of the metabolic, physical, and cognitive decline associated with ageing. It is also one of the mechanisms most responsive to intervention.
Exercise as Mitochondrial Medicine
Aerobic exercise is the most potent known stimulus for mitochondrial biogenesis, the creation of new mitochondria. Exercise activates PGC-1 alpha, often called the master regulator of mitochondrial biogenesis, which drives the production of new mitochondria and improves the efficiency of existing ones. High-intensity interval training produces particularly potent PGC-1 alpha activation and has been shown in clinical trials to increase mitochondrial capacity in older adults to levels approaching those of much younger controls. A landmark study by Sreekumaran Nair et al. at Mayo Clinic found that HIIT reversed age-related mitochondrial dysfunction more effectively than resistance training or moderate continuous exercise.
Nutritional Support for Mitochondrial Function
Several nutrients are required for mitochondrial function and are commonly deficient. CoQ10 is an electron carrier in the mitochondrial respiratory chain and its supplementation has evidence for improving mitochondrial function in deficiency states. NAD+, which declines with age, is essential for the TCA cycle and electron transport chain. Magnesium is required for ATP synthesis. B vitamins, particularly B1, B2, B3, and B5, are essential cofactors in the TCA cycle and electron transport. Lipoic acid is a cofactor in pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, key mitochondrial enzyme complexes.
- Include high-intensity intervals in your exercise programme: two HIIT sessions per week produce the strongest mitochondrial biogenesis stimulus
- Cold exposure, including cold showers, activates PGC-1 alpha and promotes mitochondrial biogenesis independently of exercise
- Support mitochondrial function nutritionally: ensure adequate B vitamins, magnesium, and CoQ10
- Avoid chronic caloric excess: mitochondria become less efficient when continuously oversupplied with substrates
- Reduce sedentary time: even brief movement breaks reduce the mitochondrial degradation associated with prolonged sitting
Sources
- Robinson, M.M., et al. (2017). Enhanced protein translation underlies improved metabolic and physical adaptations to different exercise training modes in young and old humans. Cell Metabolism, 25(3), 581-592.
- Lanza, I.R., & Sreekumaran Nair, K. (2010). Regulation of skeletal muscle mitochondrial function: genes to proteins. Acta Physiologica, 199(4), 529-547.